(a) Field of the Invention
The present invention relates to a hybrid vehicle (or a hybrid electric vehicle), and more particularly, to a method and a device for learning an engine clutch kiss point of a hybrid vehicle.
(b) Description of the Related Art
An environmentally-friendly vehicle includes a fuel cell vehicle, an electric vehicle, a plug-in electric vehicle, and a hybrid vehicle, and typically includes a motor to generate driving force.
A hybrid vehicle, which is an example of the environmentally-friendly vehicle, uses an internal combustion engine and power of a battery together. In other words, the hybrid vehicle efficiently combines and uses power of the internal combustion engine and power of a motor.
The hybrid vehicle can include an engine, a motor, an engine clutch to adjust power between the engine and the motor, a transmission, a differential gear apparatus, a battery, a starter-generator that starts the engine or generates electricity by output of the engine, and wheels.
Further, the hybrid vehicle can include a hybrid control unit (HCU) for controlling an entire operation of the hybrid vehicle, an engine control unit (ECU) for controlling an operation of the engine, a motor control unit (MCU) for controlling an operation of the motor, a transmission control unit (TCU) for controlling an operation of the transmission, and a battery control unit (BCU) for controlling and managing the battery.
The battery control unit can be referred to as a battery management system (BMS). The starter-generator can be referred to as an integrated starter and generator (ISG) or a hybrid starter and generator (HSG).
The hybrid vehicle can be driven in a driving mode, such as an electric vehicle (EV) mode, which is an electric vehicle mode using only power of the motor, a hybrid vehicle (HEV) mode, which uses rotational force of the engine as main power and uses rotational force of the motor as auxiliary power, and a regenerative braking (RB) mode for collecting braking and inertial energy during driving by braking or inertia of the vehicle through electricity generation of the motor to charge the battery.
The hybrid vehicle operates the engine clutch in order to transmit power or separate power between the motor and the engine for switching the mode. Operation hydraulic pressure of the engine clutch determining an operation of the engine clutch considerably influences drivability, power performance, and fuel efficiency of the hybrid vehicle, so that the operation hydraulic pressure of the engine clutch needs to be accurately controlled.
The operation hydraulic pressure of the engine clutch may be determined by initial hydraulic pressure by which torque is started to be transmitted as both ends of friction material of the engine clutch are in contact with each other, and feedback hydraulic pressure for adjusting the hydraulic pressure of the engine clutch by receiving feedback of speeds of the engine and the motor. The initial hydraulic pressure point may be called a kiss point.
The kiss point may be changed during the use of the engine clutch. Accordingly, it is necessary to control hydraulic pressure of the engine clutch so that the engine clutch may transmit the torque at an appropriate point by learning the kiss point.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.